Like global mean sea level (GMSL), empirical evidence indicates that the local sea level in American Sāmoa has been rising, and though the instrumental record is limited in the Pacific Island region, the rate of rise, like that of GMSL, also appears to be accelerating. As a result of the steep topography of the main American Samoan islands, the majority of the territory’s population, infrastructure, and arable land are found on low-lying coastal plains, leaving them vulnerable to inundation and increased erosion. As sea level rises, visualization tools can help coastal managers and other decision-makers plan for associated problems including salt-water intrusion of freshwater sources, inundation of valuable land and infrastructure, and loss of habitat.

To this end, and as the first part of an effort to meet the science needs of the National Marine Sanctuary of American Sāmoa, a series of passive-inundation maps depicting incrementally elevated sea levels was produced for 22 selected coastal areas of Tutuila and Aunu’u islands highlighting areas, populations, and infrastructure vulnerable to inundation. The data were then spatially analyzed to quantify land area and land cover types likely to be affected under different inundation scenarios. Of land cover types represented on Tutuila and Aunu’u, wetlands are clearly the most vulnerable, with virtually 100% of estuarine forested and estuarine scrub/shrub wetlands (in their current locations) inundated under a 2 m rise in MSL. Impervious surface and developed open space land types represent a good indication of where development is concentrated on the islands, and these two land classes both show significant inundation percentages (>10%) under 2 m of sea level rise.

R. Duncan McIntosh is a Master of Professional Science (MPS) candidate in Meteorology and Physical Oceanography at the University of Miami’s Rosentstiel School of Marine and Atmospheric Science and a Research Assistant with the East-West Center in the Pacific Regional Integrated Sciences and Assessments (RISA) program. Prior to joining the East-West Center, he earned his B.Sc. in Physics from Vanderbilt University, served three years as a US Peace Corps volunteer in Sāmoa, and single-handedly sailed across the Pacific Ocean. His research is focused on the application of spatial analysis to climate policy.